Added sysdb.git as a submodule.
Updated sysdb submodule.
Generate latest manpages from the sysdb source-code.

This is a simple approach for now which requires manual bootstrap of sysdb's
build system. Also, it does not update the sysdb submodule yet.
Added current version of the manpages.
Added sysdb.io config file for the latest manpages.
Makefile: Added man-install target.
Link all manpages from the documentation page.